New mechanisms in photo-assisted MOVPE of II-VI semiconductors

The first detailed comparison has been made of the metalorganic vapor phase epitaxy growth rates of CdTe, ZnTe, and ZnSe, measured in situ with laser reflectometry. The comparison also includes the photo-assisted growth with visible radiation from an argon ion laser. Using a standard Group II precursor (DMCd or DMZn.TEN) partial pressure of 1.5 × 10⁻⁴ atm, VI/II ratio of 1 and DIPM (M = Te, Se) the maximum growth rates are in the region of 10 to 15 AU/ s. Decrease in growth rates of ZnTe at higher temperatures or higher laser powers have been attributed to the desorption from the substrate of unreacted Te precursor. The behavior of DTBSe is quite different from DIPSe for both pyrolytic and photo-assisted growth. The maximum growth rate is around 1 AU/ s with very little photo-enhancement, except at 300°C. Secondary ion mass spectroscopy analysis of hydrogen concentration in the ZnSe layers shows high concentrations, up to 5.9 × 10¹⁹ atoms cm⁻³ for DTBSe grown ZnSe under pyrolytic conditions. These results show that the growth kinetics play an important part in the incorporation of hydrogen and passivation of acceptor doped material.     

提高E^2PROM中NMOS管源漏穿通电压的实验研究

为了提高Ｅ＾２ＰＲＯＭ中Ｎ管源漏穿通电压，用实验的方法对制造工艺进行了研究。结果表明，高能量注入是提高ＶＰＴ的有效手段，但受到ｐｎ结击穿的限制，只适用于低区短沟Ｎ管；ＤＤＤ工艺大幅度高ＶＰＴ，但ｐｎ结击穿电压低于２０Ｖ，不能应用于高压ＭＯＳ管；采用适量的防穿通注入和适当增大沟道长度为最理想的工艺途径。     

Accurate measurement of capture cross sections in deep level transient spectroscopy: Application to EL2 in GaAs

A rigorous formulation of capacitance changes during trap filling processes is presented and used to accurately determine the electron capture cross section of EL2 in GaAs at a particular temperature, 377K, in this case. The value, σ_n (377K) = 2.7 × 10⁻¹⁶ cm², is compared with that predicted from the emission dependence.     

60MHz相位介电测井仪模拟刻度器设计

文章以介电测井理论为基础，借鉴感应仪的模拟刻度方法，对大庆油田的６０ＭＨｚ相位介电井仪的模拟刻度进行了研究。参照国内外有关资料，提出了模拟刻度器的设计模型，通过理论分析与计算，建立了一套模拟刻度方法。现场初步试验，该方法取得了一定物效果，为进一步提高仪器的测量精度提供了依据。     

K_2O－B_2O_3－SiO_2玻璃成分对析晶性能的影响

本文利用ＤＴＡ、ＸＲＤ、ＴＥＭ、ＳＥＭ等技术研究了三种Ｋ２Ｏ－Ｂ２Ｏ３－ＳｉＯ２玻璃的析晶性能。结果表明，Ｋ２Ｏ－Ｂ２Ｏ３－ＳｉＯ２玻璃的析晶由分相引起，分相和析晶能力受成分影响较大。随Ｂ２Ｏ３和Ｋ２Ｏ含量增多及Ｋ２Ｏ／Ｂ２Ｏ３比值的降低，析晶加强。析晶中主晶相类别尚未查清，次晶相确定为α－方石英。     

α－Al_2O_3衬底上生长的GaN膜的光学性质

采用金属有机化学气相淀积（ＭＯＣＶＤ）方法生长了α－Ａｌ２Ｏ３衬底上外延的高质量的单晶ＧａＮ薄膜。Ｘ射线衍射光谱与喇曼散射光谱表征了ＧａＮ外延薄膜的单晶结构和单晶质量。透射光谱和光调制反射光谱定出了六角单晶ＧａＮ薄膜的直接带隙宽度和光学参数。     

Effect of site-selective substitution in bulk superconducting Tl2Ba2CaCu2O8

Magnetization measurements were carried out on bulk Tl₂Ba₂CaCu₂O₈ (referred to as Tl-2212) and on various site-selective substituted Tl-2212 samples. At 5K between 0 and 4.5 T, the 5 at. % Mg-doped Tl-2212 (Tl,Mg-2212) samples displayed enhanced pinning as demonstrated by a field dependent increase of the magnetic critical-current density J_c by 18 to 25 percent over that of pristine Tl-2212. Excess Mg (10–15 at. %), however, is deleterious. Rietveld refinement of the x-ray diffraction pattern showed Mg on the Tl sites. Auger electron spectroscopy analysis showed part of the Mg on grain boundaries. The flux-creep activation energies are higher for flux expulsion than for flux penetration in both Tl-2212 and Tl,Mg-2212 samples; the latter displays higher individual values. Our results demonstrate an increase in the number density of flux lines as a result of increased density of atomic-size-structural, defects by Mg (5 at. %) doping. In the Tl_2−yBa₂(Ca_1−zY_z)Cu₂O_8−x(z=0–0.3; single phase; x and y represent oxygen and thallium vacancies) system also studied, the T_c decreases as z increases. At z=0.3, the sample becomes an antiferromagnetic semiconductor.     

新型MTLO催化剂的研究

新型ＭＴＬＯ催化剂的研究曾健青，罗庆云，王琴，钟炳（中国科学院山西煤炭化学研究所，太原０３０００１）关键词甲醇，低碳烯烃，硫酸，二氧化锆，超强酸１引言随着石油储量消耗至尽，以煤代油的研究显得越来越重要，从合成气出发获得工业基本原料及精细化学品，已成为...     

LiMn2O4纳米粉的湿化学合成与表征

采用湿化学方法，通过水溶液中的化学反应直接合成纳米级LiMn2O4化合物，其结构基本上为无定型，但XRD图谱中已出现LiMn2O4特征峰，说明在水溶液中已初步形成尖晶石结构，运用XRD，SEM，TG－DTA等现代检测手段对样品的性能进行进行了表征，XRD及SEM等分析结果表明，合成样品经简单热处理后，晶型结构完善，形貌规整，均匀，比表面积积显著减小，粒度明显变粗。TG－DTA热分析证明，样品在低于900℃的温度下进行热处理时，仅发生LiMn2O4的晶化过程，产物的化学组成稳定，该法合成锂离子电池正极材料LiMn2O4，具有工艺流程简单，产物的成分，结构及粒度均匀等特点。     

数字图像纯位相编码分析

研究了图像傅立叶变换过程中的振幅与位相问题，突出了位相在整个变换中的重要性，并利用双位相函数对图像进行加密编码和解码，计算机模拟表明双位相编码和解码能有效的抑制附加噪声。